<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>邮件</title>
</head>
   <style>
    *{
        margin: 0;padding: 0;
    }
    canvas{
       margin-left: 30%;
       border: 1px solid #9999;
    }
   </style>
<body>
    <canvas id="tutorial"  width="800" height="600"></canvas>
</body>
<script>
    function draw(){
    var canvas = document.getElementById('tutorial')
    if(!canvas.getContext) return
    var ctx = canvas.getContext('2d')
    ctx.lineWidth=8;
    ctx.moveTo(200,200) 
    ctx.lineTo(600,200) 
    ctx.lineTo(600,400) 
    ctx.lineTo(200,400) 
    ctx.lineTo(200,200) 
    ctx.stroke()

    ctx.moveTo(200,200) 
    ctx.lineTo(400,330) 
    ctx.lineTo(600,200) 
    ctx.stroke()

    ctx.moveTo(200,400) 
    ctx.lineTo(339,290) 
    ctx.stroke()

    ctx.moveTo(600,400) 
    ctx.lineTo(461,290) 
    ctx.stroke()
    }
    draw()
</script>
</html>